北部湾涠洲岛水域发现上颌和须板异常的布氏鲸:对保护的启示

The finding of a Bryde’s whale with abnormal upper jaw and baleen near Weizhou Island in the Beibu Gulf:implication for conservation

2018年初以来,北部湾涠洲岛附近出现了布氏鲸(Balaenoptera edeni)的活动。一头上颌与须板异常的小布氏鲸个体引发热议,其视频在网络上广泛流传。我们在船只调查时,目击该个体10次,其以单独活动为主(90%),主要出现在涠洲岛到斜阳岛之间的水域,最小凸多边形家域面积为14 km^2,核心家域面积为166.9 km^2。然而,在2019年3月30日我们发现该个体已死亡漂浮在海面,根据尸体腐烂状况来推测,该个体的死亡时间大约为3~5 d,死亡原因不明。根据照片和现场解剖分析,推测该小布氏鲸的上颌和鲸须异常可能是被渔网或绳索缠绕导致的。由于无法从外形上确认属于哪一个亚种,因此我们测定了该个体的线粒体DNA D-loop(mitochondrial DNA,mtDNA)和细胞色素b(cytochrome b,Cyt b)基因,分别得到909 bp和395 bp的序列,经比对和系统发育重建,发现该个体属于近岸分布的小布氏鲸亚种(Eden’s whale,B.e.edeni)。由于小布氏鲸具有一定季节迁移特性,我们无法判断造成其上颌伤害的渔网或绳索是否在中国水域。尽管如此,仍然建议当地部门应加强宣传,减少渔网等海洋垃圾的丢弃和排放,为小布氏鲸营造一个安全的栖息环境。

In the early 2018,the Bryde’s whales(Balaenoptera edeni)began to appear around Weizhou Island in the Beibu Gulf.A Bryde’s whale with abnormal upper jaw and baleen had attracted public’s wide attention,its videos went viral on the internet.The individual had been sighted for ten times by our team,mostly(90%)occurred alone.It mainly occurred in the waters between Weizhou Island and Xieyang Island,ranging 14.0 km^2 in minimum convex polygon,and 166.9 km^2 in kernel density estimator.Unfortunately,this individual was found to be dead floating on the sea in March 30,2019.According to the carcass sighting date of March 30,and its highly decomposed status,the death date of this whale was probably between March 25 and March 27,and the cause of death was unknown.Based on analyses of photos and anatomy,the reason for its abnormal upper jaw and baleen were possibly deduced to the damage by fishing nets or cord strangle.Subspecies status of this Bryde’s whale individual cannot be identified only by morphology,thus mitochondrial DNA(mtDNA)D-loop and cytochrome b(Cyt b)were used to do the moleclar identification.Two sequences of 909bp and 395bp were obtained,respectively.Sequence blasting and phylogenetic reconstruction suggested that this individual belonged to the coastal Bryde’s whale subspecies(Eden’s whale,B.e.edeni).Because the species migrate long distance seasonlly,it was not confirmed whether this Bryde’s whale got injured by the fishing net or cord strangle in Chinese waters.Even though,the local authorities are supposed to strengthen the publicity of whale protection and reduce the disposal of marine litter,such as fishing net,and create safe habitat for Bryde’s whales.